1. Field of the Invention
The present invention is directed to a magnetic resonance tomography apparatus that contains a display device for displaying images obtained during an image registration sequence.
2. Description of the Prior Art
In many areas of technology, tomographic imaging exposure equipment is used for examination of three-dimensional objects. Some apparatuses are limited to imaging planes that are orthogonal to one another. Tomograms that are of interest, however, are often not oriented in such a way that the information content is maximal given orthogonal tomogram representation. For example, in magnetic resonance tomography the exposure of tomograms having an arbitrary orientation in space, known as double-oblique tomograms, is often required.
U.S. Pat. No. 4,871,966 discloses a method for operating a magnetic tomography apparatus for determining planes that are not positioned orthogonally to one another. On the basis of a tomogram displayed on a display device, the definition of a plane orthogonal thereto, having an arbitrarily oriented sectional line (or cut line), is effected by a linear cursor that contains a mid-point marking, which is also displayed on the display device. Using two operating elements, the linear cursor is rotated into the desired position, and the midpoint marking is guided into the midpoint of the next image to be displayed, or for which imaging data are to be obtained in a subsequent imaging sequence.
In other systems that allow the representation of arbitrarily arranged planes, the definition of the planes takes place, for example, via keyboard entries or one-handed control relative to the last tomogram, for example using a 6D trackball or 6D cursor, or via the input of three points in space. These methods must be learned by the operator, require habituation, and require a high degree of spatial conceptualization on the part of the operator.
The object is inventively achieved in a magnetic resonance tomography apparatus having a device whose spatial orientation can be modified and whose spatial orientation defines a plane having a particular spatial orientation, whereby the spatial orientation of a tomogram inside a three-dimensional exposure subject is defined.
The object is inventively achieved in the magnetic resonance tomography apparatus having a device whose spatial orientation can be modified and whose spatial orientation defines a plane having a particular spatial orientation, whereby the spatial orientation of a tomogram inside a three-dimensional exposure subject is defined.
This apparatus produces an intuitive operation. For example, by a manual variation of the spatial orientation of the device, the operator achieves a selection of a corresponding spatial orientation of a tomogram in the exposure subject.
In an embodiment, the spatial position of at least one point of the apparatus defines the spatial position of the tomogram inside the three-dimensional exposure subject, and the spatial position of at least the one point of the device can be modified. In this way, besides the spatial orientation of a tomogram in the three-dimensional exposure subject, the spatial position of the tomogram is defined using the same device, and the tomogram is thereby unambiguously defined. In mathematics, a plane is determined unambiguously by a point and a vector collinear to the normal unit vector of the plane (i.e. a vector perpendicular to the plane and having magnitude equal to (with an absolute value of one). In relation to the inventive apparatus, this means that the spatial orientation of the device defines the direction of the normal unit vector of the tomogram, and the spatial position of the device defines a point of the tomogram.
In a further embodiment, the spatial orientation of the device before a tomogram exposure defines a tomogram to be exposed inside the three-dimensional exposure subject. In this way, only very few well-directed exposures are required for achieving the display of the desired tomogram. This results in a short overall exposure time for an exposure subject. In magnetic resonance tomography apparatuses in particular, which enable very short exposure timesxe2x80x94for example a few hundred millisecondsxe2x80x94per tomogram, each modification of the spatial orientation of the inventive device is advantageously accompanied by a corresponding tomogram exposure and display, so that between the definition and the display of a tomogram there is a time delay that is not perceivable by the operator, or is only slightly perceivable. The above-cited real-time tomogram imaging in connection with the inventive device facilitates the intuitive definition of the tomograms for the operator.
In another advantageous construction, the spatial orientation of the device defines a tomogram that is to be displayed on the display monitor inside a three-dimensional data set. In this way, the inventive device allows an intuitive, simple and rapid definition of the spatial orientation and position of tomograms that are to be displayed, even for already-exposed three-dimensional data sets.
In another embodiment, the device has a flat stamped part, or is a plate that determines the plane. For assisting spatial conceptualization, a plate is the most obvious choice for the representation of a corresponding plane or a tomogram, and thereby facilitates the definition of the spatial orientation.
In a further embodiment, the device whose spatial orientation is modifiable is the display device itself of the magnetic resonance tomography apparatus, whose display surface defines the plane. In this way,.an existing component of the apparatus, as well as the flat stamped part of the display surface, are used for the realization of the inventive device.
In another embodiment, the display device is a liquid crystal display screen. Compared to a cathode-ray tube display device, a liquid crystal display screen is substantially more compact and lighter, and thus is more easily modified as to its spatial orientation and position. The planar character of a liquid crystal display screen makes it easier for the user to conceptualize the orientation and position of the plane of section.
In a further embodiment, the spatially modifiable device has an oblong stamped part that is perpendicular to a plane and thus defines that plane. This definition of the spatial orientation of a tomogram, by the oblong stamped part of the device defining, as a straight line, the direction of the normal vector, is more abstract than is the case given a planar stamped part of the device, but provides more freedom in the construction of the inventive device.
In another embodiment, the spatially modifiable device is not connected to the imaging apparatus, or at least is not permanently connected to it. This achieves the greatest possible freedom of motion for the device.
In another embodiment, the spatially modifiable device is fastened to a carrier or support device that contains at least one joint and at least one support element. The (at least one) support element of the carrier device may, for example, be a telescoping support. The presence of a carrier device facilitates the acquisition of the position of the spatially modifiable device, and the defined tomogram orientation is kept visible at all times in relation to a device that is not connected to the apparatus, or at least is not fixedly connected to it.
In another embodiment, the spatial orientation and position of the device are acquired via sensors attached to the device or to the carrier device. The sensors may be optical sensors, for example. An optical acquisition of position is advantageous in particular given very high demands on electromagnetic compatibility.